Active voltage balancement of series connected IGBTs

Series connection of IGBT devices is a standard solution in high voltage power conversion applications, such as color TV deflections, inverters for medium voltage lines or modern railway traction drives. In serial connections of IGBTs, a suitable voltage balance must be guaranteed either at steady state or during switching transients in order to avoid damaging overvoltages. In the present paper, a new approach is proposed in order to equalize the voltage distribution between series connected IGBTs during turn-off transients by controlling the gate capacitance charge profile. The main advantages of such an approach consist in avoiding the use of passive components on the power side and in working exclusively on the gate driving signals. The effectiveness of the proposed approach is verified by simulation and experimental tests.